Search

Bacterial production, respiration and metabolic diversity were measured up to 120 m depth in the Sub-Antarctic Front (SAF) and Polar Fronts I and II (PFI and PFII) of the Indian Ocean sector of the Southern Ocean during 2010 Austral Summer. Prokaryotic cell count was maximum at PFI and PFII (~109 cells L−1) and minimum at SAF (~107 cells L−1). Furthermore, integrated bacterial production was higher at PFI (1.07 mg C m−2 h−1) and PFII (0.72 mg C m−2 h−1) compared to SAF (0.61 mg C m−2 h−1). At PFII, integrated bacterial growth efficiency was higher (8.96) compared to PFI (7.42) and SAF (7.17), signifying that the net contribution of PFII to the microbial loop could be relatively pronounced. Enhanced cell numbers and production at polar fronts indicate that the dissolved organic matter could be converted to secondary biomass through the microbial loop. However, integrated bacterial respiration rate at PFII (0.83 mg C m−2 h−1) was lower than that at PFI (1.84 mg C m−2 h−1) resulting in higher growth efficiency at PFII. Metabolic flexibility at SAF was clearly brought about by utilization of carboxylic acids like D-malic acid and itaconic acid, and carbohydrates like N-acetyl D-glucosamine, D-cellobiose and D-lactose. Utilization of amino acids like glycyl L-glutamic acid and L-threonine, and an amine, phenylethylamine, was critical in determining the metabolic variability at PFI. PFII hosted microbes that utilized phenolic compounds (2-hydroxy benzoic acid and 4-hydroxy benzoic acid) and polymers (like Tween 80). Utilization of polyols over carbohydrates in polar waters indicates a niche with lesser influence of the Antarctic melt waters on the bacterioplankton metabolism.

This study addresses factors governing nitrification and denitrification rates, along with the abundance of the bacterial groups likely involved in these activities, in Kongsfjorden, an Arctic fjord at Ny-Alesund, Svalbard. The fjord was sampled three times during the month of March 2008 as day length and direct solar radiation increased. Although initially well mixed, cooler and more saline, the fjord became stratified, warmer and less saline during late March. The concentrations of NH4 + (4.4 ± 1.6 to 6 ± 1.6 μM) and NO2 − (1 ± 0.3 to 1.2 ± 0.4 μM) increased progressively with the decrease in NO3 − (6.1 ± 1.3 to 3.8 ± 1.5 μM), reflecting the onset of primary productivity. Nitrification rates and the culturable population of nitrifiers decreased significantly from 1.6 ± 0.9 to 0.4 ± 0.1 ng at NH4 +-N l−1 h−1 and 5.1 ± 0.3 × 102 to 29 ± 14 cells l−1, respectively. In contrast, denitrification rates increased (2.4 ± 0.5 to 4.6 ± 1.3 ng-at NO3 −-N l−1 h−1), although the abundance of culturable denitrifiers did not vary significantly. A significant correlation of nitrifiers with NO3 − during early March (p

The year 2012 began with reports on the completion of drilling over the largest subglacial lake of Antarctica, Lake Vostok. It has been sealed from free exchange with the atmosphere for ∼420,000 years, making it a potentially rich and largely unexplored storehouse of genetic information for solving evolutionary queries. Indirect evidence suggests that many impediments exist in the subglacial environment, such as high oxygen tension, low inorganic and organic nutrient concentrations, etc., whereas analysis of glacial and accretion ice from Vostok also implies that the elemental requirements for microbial growth could be satisfied in the lake by many possible electron donors (like H2, Fe2+ and NO 2 − ). Recent reports on the recovery of the longest ever ice core of ∼3,769 m open up a new window for answering many questions about microbiological life in extremes, evolution, and adaptations. This review attempts to present an updated understanding on the potential significance of subglacial environments in unraveling the mystery of evolution of life.

We report the expression pattern of heat shock proteins (HSPs) in an Antarctic psychrotrophic strain of Cellulosimicrobium cellulans (DSM 22151) by comparing with its mesophilic counterpart (DSM 43879T) at different temperatures. In both strains, the synthesis of HSPs declined with growth phase. The Antarctic isolate could upregulate 60 kDa, 52 kDa and 41.6 kDa HSPs at 60°C while for its mesophilic counterpart, regulation was restricted to a 64 kDa fraction. The highly unstable nature of this fraction could have led to the impaired thermotolerance exhibited by the mesophilic strain. The downshift of thermal shock from 60°C to 45°C resulted in further upregulation of HSPs in the psychrotrophic strain, while there was no marked variation in the mesophilic strain. This work highlights the significance of a 60 kDa protein in the Antarctic strain of C. cellulans and also indicates the role of a 52 kDa protein in the previously reported heat shock response. Contrary to expectations, the psychrotrophic strain was found to have better mechanisms to tolerate higher temperatures—a property that could give valuable insights into the evolution and adaptation of cold-adapted bacteria.